Determination of Iron Active Sites in Pyrolyzed Iron-Based Catalysts for the Oxygen Reduction Reaction
Determination of Iron Active Sites in Pyrolyzed Iron-Based Catalysts for the Oxygen Reduction Reaction
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DOI：
10.1021/cs300579b
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发表时间：
2012-12-01
期刊：
影响因子：
12.9
通讯作者：
Chen, Zhongwei
中科院分区：
文献类型：
--
作者：
Li, Wenmu;Wu, Jason;Chen, Zhongwei
铁基氧还原反应（ORR）催化剂材料被认为是传统铂基催化剂的有前途的非贵重替代品。这些催化剂材料通常是通过高温热解处理现成的碳、氮和铁源生产的。在热解过程中，对结构和活性位点形成的充分控制几乎是不可能的。因此，这些材料中催化活性位点的化学性质、结构和ORR机制是一个有重大争议的主题。我们提出了一种方法，利用CN-离子作为铁基催化剂上的ORR抑制剂，以深入了解催化活性位点的确切性质和化学性质。此外，我们提出了高温热解处理过程中两种可能的催化活性位点形成机制，这取决于前驱体的具体类型和所采用的合成方法。利用ToF-SIMS负离子和正离子成像，我们进一步提供了我们提出的活性位点形成的直接证据。这些知识将有助于未来开发具有改善ORR活性和运行稳定性的铁基催化剂，用于燃料电池和电池的应用。
Fe-based oxygen reduction reaction (ORR) catalyst materials are considered promising nonprecious alternatives to traditional platinum-based catalysts. These catalyst materials are generally produced by high-temperature pyrolysis treatments of readily available carbon, nitrogen, and iron sources. Adequate control of the structure and active site formation during pyrolysis methods is nearly impossible. Thus, the chemical nature, structure, and ORR mechanism of catalytically active sites in these materials is a subject of significant debate. We have proposed a method, utilizing CN- ions as ORR inhibitors on Fe-based catalysts, to provide insight into the exact nature and chemistry of the catalytically active sites. Moreover, we propose two possible catalytically active site formation mechanisms occurring during high-temperature pyrolysis treatments, dependent on the specific type of precursor and synthesis methods utilized. We have further provided direct evidence of our proposed active site formations using ToF-SIMS negative and positive ion imaging. This knowledge will be beneficial to future work directed at the development of Fe-based catalysts with improved ORR activity and operational stabilities for fuel cell and battery applications.